Overview

This is a draft protocol. This will be optimized to measure transcriptional response from the pheromone and hyperosmotic stress pathway in S. cerevisiae

Solutions

FISH Probes

Fish probes are designed using the probe designed from BioSearch technologies and ordered from BioSearch technologies.

Reconstituting the Dried Probe Stock

The probe stock should be sufficient to provide up to 200 or more hybridizations. For frequent use, aliquots of the probe stock can be stored at +2 to +8 °C in the dark for up to a month. Redissolve the dried oligonucleotide probe blend in 200 μL of T10E1 buffer (10 mM Tris-HCl, 1 mM EDTA, pH 8.0), to create a probe stock at a total oligo concentration of 25 μM. Mix well by vortexing and spin down.

Storage of the Reconsistuted Probes

Short-Term Storage & Daily Use

Dissolved probe mix should be subjected to a minimum number of freeze-thaw cycles.
For daily and short-term use, the mix can be stored at 4°C in the dark for up to a month.

Long-Term Storage

Store the probes in the dark at -20°C for storage lasting longer than a month.

Buffer B

1.2M Sorbitol

100mM KHPO4 pH 7.5

To make mix together:

8ml of 1M KH2PO4

41.5 ml of 1M K22HPO4

Sorbitol 109.3g

β-Mercaptoethanol

Fisher O3446I; Stored in the flammables cabinet.

Concanavalin A Solutions

DAPI Stock Solution

DAPI, dilactate, catalog #D9564 from Sigma

To make a 5 mg/mL DAPI stock solution (10.9 mM for dilactate), dissolve the contents of one vial (10 mg) in 2 mL of deionized water (dH2O).
Note: This DAPI derivative is not very soluble in phosphate-buffered saline (PBS).

Storage: For long-term storage the stock solution can be aliquoted and stored at ≤–20°C. For shortterm
storage the solution can be kept at 2–6°C, protected from light. When handled properly, DAPI solutions are stable for at least six months.

Vanadyl Ribonucleoside Complex (VRC)

New England Biolabs, S1402S

Aliquoted and stored in the -20°C freezer. Stock solution is 200mM. Defrost the frozen stock from the freezer at room temperature. This can be reconsistuted to a green-black clear solution by incubating the tube at 65°C only if necessary.

NOTE: Mix together 0.85 mL of nuclease-free water and add 100 µL of 20X SSC, 40 µL of 10% glucose and 10 µL of 1 M Tris-HCl. Vortex and then transfer 100 µL of this “GLOX” buffer to another tube, to which one should add 1 µL of the glucose oxidase stock and 1 µL of mildly vortexed catalase suspension. The remainder can be used as an equilibration buffer.

NOTE: Mix together 0.85 mL of nuclease-free water and add 100 µL of 20X SSC, 40 µL of 10% glucose and 10 µL of 1 M Tris-HCl. Vortex and then transfer 100 µL of this “GLOX” buffer to another tube, to which one should add 1 µL of the glucose oxidase stock and 1 µL of mildly vortexed catalase suspension. The remainder can be used as an equilibration buffer.

Protocol

Fixing Cells

Grow culture to Klett ~50-100 in LFM media (can also use YPD or SC media). If you are measuring OD, grow cells to an OD of ~0.4-0.6

Fix cells by adding 32% paraformaldehyde directly to the culture to a final concentration of 6.4% (4ml culture + 1ml paraformaldehyde). Incubate at room temperature for 45 minutes.

Spin the cells down at 3000 xg for 5 minutes. Resuspend in 1.8 ml Buffer B and transfer to a 2 ml eppendorf.

Wash cells 3X with 1.8ml Buffer B by pipetting up and down gently. Spin down at 3000 xg for 5 minutes each time.

Incubate at 37°C. Monitor the digestion every 10 minutes or so. Check the cells on the small scope by the nanodrop. Once you reach ~90% phase dark (digested) cells the digestion is done. The first time you try the protocol, this step will need to be optimized. Previous attempts suggest that about 15 minutes works well.

Spin 5 min at 3000 xg (do not spin too hard as cells are fragile due to lyticase).

Incubate at 4°C overnight. Cells can be stored like this for about a week before hybridization (perhaps longer, this would need to be tested. The Botstein lab protocol seems to indicate that cells can be stored in this state at -20°C for up to several months).

Hybridization

Mix a small volume of the probe stock (1µL) with Hybridization Buffer to 100 µL final volume for each sample to be hybridized. Vortex and centrifuge the probe solution(s) briefly.

For the initial test of a probe-set it is best to start 4 separate hybridization reactions to determine which dilution of the probe stock is optimal for detection. Add 1 µl from each of each of the working dilutions (1:10, 1:5, 1:2.5) as well as the probe stock itself into separate aliquots of the hybridization solution. The working dilutions should be made into T10E1 (same as for the initial resuspension of the dried probe).

Gently aspirate the 70% ethanol off of the sample.

Add 1000μL of wash buffer with the same percentage formamide (10%) as the hybridization buffer and let stand for 2-5 minutes.

Spin 10 min at 2000rpm, aspirate the SSC and add the GLOX buffer without enzymes 1ml for equilibration; incubate for 1-2 minutes.

Spin 10 min at 2000rpm, aspirate the buffer and add 100 µL of GLOX buffer to which the enzymes (glucose oxidase and catalase) have been added.

Proceed to imaging

Image

Coat the 96 well optical plate with POLY-L-LYSIN solution, incubate at room temperature for 5 minutes, aspirate the solution, dry for 30 minutes in room.

Wash with water 3X and dry for 30 minutes in room.

Add cells in the GLOX buffer to the well and wait 30 minutes for the cells to settle down.( The amount of cells depends on the cell pellet you have before you add the GLOX buffer.)

Gently aspirate the buffer and wash with 1X PBS 3 times and then wash with 70% ETOH.

Cover the well with 50 µL of ProLong Gold Antifade Reagent proceeds to the scope.

Notes

Please feel free to post comments, questions, or improvements to this protocol. Happy to have your input!

*Megan N McClean The Buffer B protocol is not exactly 1.2M sorbitol because the volume of the sorbitol added is not taken into account, similarly the KHPO4 concentration is slightly less than 100mM. This is the protocol that the Botstein lab uses, so I'm assuming that it works fine.

*Megan N McClean This protocol is in the process or being optimized. Steps that may need to be modified (there may be more, this is just what I can think of at the moment):

DAPI concentration

Megan N McClean 17:27, 19 October 2011 (EDT): Some notes from Sandy in the Botstein lab:

He uses 10mls of about 3x107== chemostat cells to start off with, spins those down and they end up in 1ml of 70% EtOH at the end of the first day, and then he takes 300μL of that to proceed to the hybridization steps. He does all of the hybridization steps in tubes, and does all of the washes with 1ml and then spins very gently (2000rpm on the Botstein small brown centrifuge). After our step 13 (was and resuspend in 2x SSC he does another spin down and resuspend and wash in 1x SSC.

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